Lean Body Mass Calculator

Lean body mass is the foundation of body composition. It's what you want to build (in a bulk), preserve (in a cut), and track over time as the indicator of successful training. Unlike body weight, which fluctuates with water, food, and waste, changes in lean body mass reflect actual changes in muscle tissue — slow, meaningful progress.

From a metabolic standpoint, LBM is the primary determinant of your resting metabolic rate. Skeletal muscle burns approximately 6 kcal/pound/day at rest, compared to about 2 kcal/pound/day for fat. Building 10 lbs of lean mass raises your BMR by roughly 60 calories per day — modest individually, but meaningful over years of consistent training.

For weight loss, the goal should be to lose fat while preserving LBM as much as possible. The combination of high protein intake and resistance training during a caloric deficit accomplishes this better than any other strategy. Studies comparing high-protein groups to low-protein groups in identical caloric deficits consistently show the high-protein group preserves significantly more muscle while losing similar amounts of fat.